Objective: To analyzed a large group of invasive breast cancers with long-term follow-up information to evaluate the clinicopathologic, morphological and prognostic features of basal-like breast cancers in Chinese population.
Methods: Immunohistochemistry was used to detect the expression of ER, HER2, CK5/6, EGFR on tissue microarray with 1311 invasive breast cancers. Based on the results, these cases were categorized into luminal A, luminal B, basal-like, HER2-overexpressing and null subtypes. Clinicopathological features and survival rates were compared between these groups.
Results: Basal-like breast cancers constituted 17.0% of 1311 invasive breast cancers with a significantly larger size, higher grade and higher incidence of the medullary carcinoma, frequent recurrence and infrequent node metastasis. Morphologically, basal-like breast cancers showed a significantly more solid architecture and ribbon-like architecture associated with necrosis (more geographic necrosis) and central scar, a more pushing margin, lymphocytic infiltration and a higher mitosis score, more syncytial growth, presence of basaloid cells, spindle cells and squamous metaplasia. The disease-free survival and overall survival of basal-like breast cancers were significantly poorer than that of luminal A subtype, but similar to the other ER-negative subtypes. Basal markers were not independent prognostic factors.
Conclusions: Basal-like breast cancers in Chinese population has a similar prevalence to that of the western populations. They have distinct clinicopathologic features compared to other non-basal breast cancers, but overlapping with other ER-negative breast cancers. Morphological features are strongly associated with basal-like breast cancers although they are not very specific. The survival of basal-like breast cancers is poorer than luminal A, but similar to the other ER-negative breast cancers, and basal markers are not independent prognostic factors of breast cancers.